The conventional electric jogging machine comprises a support frame and a trotting platform. The support frame is formed of a base and a support body extending upward from the base. The two opposite sides of the front end of the trotting platform are fastened pivotally with the support body. The underside of the rear end of the trotting platform is provided with two feet in contact with the floor surface. The conventional jogging machine is folded by lifting the rear end of the trotting platform, which is then turned on the two pivoting points of the front end of the trotting platform to join with the support body. The center of gravity of the conventional electric jogging machine is relatively high in view of the two pivoting points being apart from the floor surface by a considerable distance. As a result, the jogging machine in operation is apt to sway, thereby making its user uneasy and jittery. In addition, the trotting platform is manually slanted to accommodate its user to emulate an uphill jogging. The manual adjustment of the trotting platform is conceivably inconvenient to its user who is in the midst of doing the jogging exercise.
The U.S. Pat. No. 6,050,923 discloses a foldable jogging machine, which is free from the shortcomings of the conventional electric jogging machine described above and is formed of a trotting platform and a triangular support mechanism for supporting the trotting platform. This prior art jogging machine is defective in design in that its trotting platform is considerably heavy and is therefore susceptible to vacillation.